Means for heating thermoplastic materials for molding



July 25, 1944.

A. ALVBURRY 2,354,363

MEANS FOR HEATING Tni'znmorm'iic MATERrALs FOR MOLDING '2 Sheets-Sheet 2Filed April 23, 1943 [rm enter. v Ar/Aur'A.Burr

Patented July 25,

UNITED STATES PATENT OFFICE MEANS FOR HEATING THERMOPLASTIC MATERIALSFOR MOLDING Arthur A. Barry, Toronto, Ontario, Canada Application April23, 1943, Serial No. 484,296

8 Claims. (Cl. 1830) This invention relates to improvements in theconstruction of the means'for heating thermoplastic material as it isfed to the molds or dies,

and the principal object of the invention is to provide an apparatuscapable of operation free from leakage of the heating medium underexcessive temperatures and pressures and to devise a structure which maybe manufactured at reasonably low cost and which will ,be.simple andeasy to assemble.

The principal feature of the invention consists in the novelconstruction and arrangement of a hollow core to be supported within acylinder through which the thermo-plastic material is forced which issurrounded by a sealed jacketprovided with an immersion electric heatingunit arranged at the bottom thereof below the bottom of the cylinder togenerate steam and, eflect the continuous flow thereof around thecylinder to create and maintain a substantially uniform temperaturesurrounding the cylinder to plastify the contents thereof, wherebycommunication between the steam jacket surrounding the cylinder and theinterior of the core is maintained through ducts formed in the cylinderregistering with ducts formed in the core and communicating with thecentral chamber thereof, the sealing of the juncture of the ducts of thecore and the cylinder body being effected with compression sealing. Inthe accompanying drawings I Figure 1 is a longitudinal mid-sectionalview of a thermo-plastic heating cylinder constructed in accordance withthis invention, the section being made on the line l-l of Figure 2.

Figure 2 is a transverse section of the device taken through the line2'2 of Figure .1.

hollow steam-heated core is disclosed in my 00- pending application No.308,549, of December 11, 1939, now U. S. Patent No. 2,319,439, dated May18, 1943.

Certain classes of thermo-plastic material and the molding of certainarticles from 'thermoplastic material require extremelyhigh-temperatures and pressures. and the present invention has beendevised in order to obviate leakage of the heat-transmitting fluid inthe form of high pressure steam.

In the construction herein illustrated the cylinder I, in which theplastic material. is confined,

'is surrounded by a cylindrical jacket 2 which isspaced from the outersurface of the cylinder and is provided with intumed end flanges 3 and lwhich form a sealed joint with the outer surface Figure 3 is anelevational view of the discharge nozzle end of the device partly brokenaway.

Figure 4 is a longitudinal sectional view of the nozzle end of thecylinder taken on the line 4-4 of Figure 2.

Figure 5 is an eievational detail of the inward end of the core.

Figure 6 is a transverse section on the line 6-0 of Figure 1. 1

In my United States Patent 2,115,940, dated May 3, 1938, I disclosed aPlastic injection device in the form of a cylinder having a dischargeorifice and provided with pressure. means for ejecting the cylindercontents with the cylinder surrounded by a sealed jacket spacedtherefrom and in which an immersion electric heating unit was arrangedat the bottom of the jacket below the bottom of the cylinder, saidjacket containing a body of water surrounding the heater whereby steameter of the cylinder.

of the cylinder wall. The jacket and the cylinder are assembled with atight driving fit and, being both constructed of metal of the samecoefficient of .expansion, a-pressure tight joint is ef'-' fected aseach of the flanged ends of the jacket are under extremely highpressures and tem peratures. v

The end of the jacket remote from the discharge end of the cylinder isprovided with a transverse chamber 5 which extends below, the

bottom of the interior of the jacket 2 and supported therein is anelectric heating element 6 which is immersed in a body of water 1. Whencurrent is applied to the heating element 6 steam is generated and thiscirculates around the perimeter of the cylinder i and maintains aconstant application of temperature to' the entire perim- It will beunderstood that owing to the ex- .treme elasticity of steam the instantthat heat is absorbed therefrom it willbe replaced by the constantlycirculating steam body and condensation will immediately return to theheating chamber 5. This principle has been, effectively proven inextensive commercial use of heaters made in accordance with my PatentNor 2,115,940.

It has been found expedient to provide a dome cess through the orificell.

plugs 28.

to the'steam chamber and this is arranged in the form of a recess 8formed in the topside of the jacket 2, preferably above the chamber I,and a suitable gauge I is connected with this re- An orifice II isprovided for the purpose of inserting .water into the device and this isclosed by a suitable plug it.

In the bottom of the chamber are arranged a pair of obliquely disposedorifices l3 and H.

These are closed by suitable'safety fuse plugs II which may be an'angedto blow at any desired maximum pressure.

At the nozzle or discharge end of the the cylinder wall is drilledinwardly from the ends to form a plurality of ducts l8 which connectwith radialducts H which open through the outer wall of the, cylinderinto the space enclosed by the jacket 2 so that a plurality of ductscommuto the end of the cylinder. The end of each of the ducts II iscounterbored,. preferably. with a taper counterbore II and into each ofthese counterbores is fitted a compression seal is in the form of aferrule of copper or other suitable ductile metal.

The end face of the cylinder is formed with a counterbore 20. .Acircular head 2|, adapted to fit snugly into the counterbored end of thecylinder l, is provided with a cylindrical core extension '22, 'theouter perimeter of which is spaced from the inner wall of the cylinderI. is preferably pointed at its inner end to direct the thermo-plasticmaterial outwardly between the outer wall of the core and the inner wallof the cylinder. The core is preferably supported adiacent to its inner'end by suitable fins 23.

The face of the head which engages the counterbored end face of thecylinder! is formed.

This core asisascs.

cylinder nicate with the steam jacket and lead outwardly lating steamthrough this wall to plastify the material as it is forced through theannular passage between the core and the cylinder wall.

The head II is formed to fit snugly into the counterbores of the end ofthe cylinders and it is secured firmly in position by a plurality of capscrews 33 which are threaded into threaded holes 34 arranged in the endof the cylinder and spaced between the ducts II.

It will.be readily appreciated that the closefitting surfaces of thehead I and cylinder ends will prevent the escape of the thermo-plasticmaterial that is being forced through the cylinder and the compressionseals it may be compressed by the tension of the cap screws 33 tmholdany required pressure of steam that may be used in sealing the ductscommunication between the steam jacket and the interior of the core.

with tapered counterbored recesses '24 which register with thecounterbored recesses It in the end of the cylinder and which receivethe projecting ends of the compression seal members I! when the head isplaced in position. The compression seal members are bored andcommunicate with holes 25 which are aligned with the ducts l6 by thecompression sealing members.

Diagonal ducts flare bored in thehead If to communicate with the outwardends of .the holes 25 and open inwardly into the hollow interior 21 ofthe'core 22, the outer ends of -'the ducts 2| beyond the holes ll aresealed with suitable From this description it will be understood that aplurality of ducts form communicating passages with the steam jacketsurrounding the cylinder and the centre of the core 22,- and steamentering the chamber 21 of the core circulates freely and condensationwill be carried out through the lower duct into the bottom of the steamjacket to find its way to the steam-generating chamber described.

The head :1 is provided with a t 'ed coun- It will be understood fromthisdescription that the structure of the device is simple and it may bemanufactured'very readily at very moderate cost.

When the cylinder and head are machined and readyfor assembly theconical compression seals are simply inserted in the counterboredrecesses,

the head and cylinder are placed together-and the cap screws are drawnup tight to complete theseal concurrently of the cylinder and the steamjacket and p ssages.

With a device such as described extremely high temperatures may beapplied to plastify the thermo-plastic material without danger ofburning the material and a constant anduniform condition of molding maybe maintained.

It is found desirable to provide for the release of air which may betrapped within the steam chambers. and I provide a pipe 35, preferablyinserted into the dome 8 and provide same with a suitable valve (notshown) to facilitate such removal. v

What I claim as my invention is:

l. A means-for heating thermo-plastic materials for molding, comprisinga cylinder having an open end surrounded by a steam jacket, saidcylinder havin ducts formed therein communicating with the steam jacketand leading to an end surface, a head closing the open end-oi thecylinder and having a hollow core extending terbore 2! which has acentral conicalprojec- 'tion 3. and a plurality of holes 3| are boredthrough the head portion in groups arranged between the ducts It andleading from me annular space between the inner cylinder wall and theexternal wall of the core 22. These holes are shown in the form ofgroups of tapered holes but they may constitute open passages and theyare aligned with the tapering wall of the conical projection 130 so thatthe thermo-plastic material which .is forced through the cylinder fiowsout through the tapered holes or passages and around the conicalprojection ll; A suitable nozale I! is 18 into and spaced from thecylinder wall, said head having ducts communicating with the ducts inthe cylinder andleading into the hollow core. and means for pressuresealing the juncture of the'ducts of said cylinder with the ducts ofsaid head. I

2. A means for heating thermo-plastic materials for molding, comprisinga cylinder having an open end and surrounded with a steam'iacket andhaving ducts formed therein leading from the steam jacket to the openend of the cylinder,

a head abutting the open end of the cylinder and having a hollow coreextending into the cylinder, ducts in the head aligned with the ducts inthecylinder wall and leading inwardly to the hollow core, the adjacentmeeting end'sof saidcylinderand head ductsbeing counterbored, per- I 73,854,868 forated compressible sealing members seated insaidcounter-bores and joining the ducts, and

' means for drawing the head into sealed contact with the end of thecylinder.

3. Adevice as claimed inclaim .2 in which the co'unterbores in theadjacent meeting ends of the head and cylinder ducts'are tapered, thecompressible sealing members being in the form of tapered metallicferrules inserted in said counterbores and pressed into sealingengagement therewith. 4. A device as claimed in claim 1 in whichpassages leading from the interior of the cylinder extend through thehead between the ducts connecting the steam jacket with thehollow core,

said passages leading to a discharge orifice in the head. Y

5. A device as claimed in claim 1 in which the head is formed with acounter-bored recess in its outer side provided with. a central conicalextension and passages lead inwardly from the base of said conicalextension through the head and spaced therefrom, I ducts communicatingwith the hollow interioroi the core and'leading outwardly to align withthe ducts extending from the steam jacket through the end of thecylinder, the interior oi the core being in cylindrical form and havingconical ends and the exterior ends of the core being conical, means forcompression sealing the adjoining ducts of the cylinder and head, andmeans forv securing said head in compression sealing contact, said headhaving discharge orifices leading from the interiorof the cylinder.

'7. Means for heating theme-plastic materials I formolding,..comprisinga cylinder having 'an open end and a steam Jacket therearound and havingducts arranged at the top and bottom leading from the steam jacket to anend surface of the cylinder, a head engaging in sealing steam jacketthrough'the open end of the cylinder, a head closing the end of thecylinder hav- .iack'et. ing a hollow core extending into the cylindercontact with the open end ofthe cylinder and having a reduced coreextension projecting into the cylinder'and spaced from the cylinder andhaving a pointed end, ducts formed in the head registering with theducts in the cylinder and leading to the hollow core, means for pressuresealing the adjacent ends of the cylinder and head ducts, cap screwsthreaded into' the cylinder extending through the head and clamping thehead to the cylinder end in sealed contact,-

" and discharge passages arranged in said head leading to a commondischarge orifice from the interior of the cylinder.

8. A device as claimed in claim 1 having an air release duct leadingfrom the top of the steam ARTHUR A. HURRY.

